CA1182857A - Ignition method and igniter device for ignition carburated gaseous mixtures - Google Patents
Ignition method and igniter device for ignition carburated gaseous mixturesInfo
- Publication number
- CA1182857A CA1182857A CA000393083A CA393083A CA1182857A CA 1182857 A CA1182857 A CA 1182857A CA 000393083 A CA000393083 A CA 000393083A CA 393083 A CA393083 A CA 393083A CA 1182857 A CA1182857 A CA 1182857A
- Authority
- CA
- Canada
- Prior art keywords
- dielectric
- face
- high voltage
- electrode
- electrodes
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000008246 gaseous mixture Substances 0.000 title claims abstract description 16
- 238000000034 method Methods 0.000 title claims description 11
- 239000000203 mixture Substances 0.000 claims description 15
- 238000002485 combustion reaction Methods 0.000 claims description 14
- 238000004519 manufacturing process Methods 0.000 claims 1
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- 239000007789 gas Substances 0.000 description 8
- 239000003989 dielectric material Substances 0.000 description 3
- 230000005684 electric field Effects 0.000 description 3
- 239000012212 insulator Substances 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 2
- 238000010892 electric spark Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000005524 ceramic coating Methods 0.000 description 1
- 210000003298 dental enamel Anatomy 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- QHGVXILFMXYDRS-UHFFFAOYSA-N pyraclofos Chemical compound C1=C(OP(=O)(OCC)SCCC)C=NN1C1=CC=C(Cl)C=C1 QHGVXILFMXYDRS-UHFFFAOYSA-N 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 230000000284 resting effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P15/00—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits
- F02P15/08—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits having multiple-spark ignition, i.e. ignition occurring simultaneously at different places in one engine cylinder or in two or more separate engine cylinders
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T13/00—Sparking plugs
- H01T13/52—Sparking plugs characterised by a discharge along a surface
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Spark Plugs (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Flash-spark plug device of the type sliding on an iso-lator surface for igniting carburated gaseous mixtures comprising-a high voltage electrode, at least a ground electrode, at least a high resistivity dielectric elongated member. The dielectric member has a face exposed to be carburated gaseous mixture and the electrodes are in intimate contact with this face and define a dielectric gap thereon. Means is provided for applying a pulsed high voltage across said electrodes. At least a conductive strip lying on the face of the dielectric member opposite to the exposed face and terminating in the region of said face located substantially beneath said high voltage electrode is connected to the ground electrode.
Flash-spark plug device of the type sliding on an iso-lator surface for igniting carburated gaseous mixtures comprising-a high voltage electrode, at least a ground electrode, at least a high resistivity dielectric elongated member. The dielectric member has a face exposed to be carburated gaseous mixture and the electrodes are in intimate contact with this face and define a dielectric gap thereon. Means is provided for applying a pulsed high voltage across said electrodes. At least a conductive strip lying on the face of the dielectric member opposite to the exposed face and terminating in the region of said face located substantially beneath said high voltage electrode is connected to the ground electrode.
Description
The invention relates to igni-tion by elec-tric spark plugs of gaseous carburated mixtures used in internal combustion engines, evaporated fuel burners of industrial boilers, gas turbines and ramjets, and more particularly to creeping dis-charge spark plugs of the flash-spark type in which the spark creeps over the surface of an insulator to ignite the mixture of gases in a combustion chamber.
Known methods of electrical ignition consist in bring-ing about an electric spark at the appropriate moment in a gaseous medium in order under certain conditions to achieve ignition and to maintain combustion.
As a general rule, the spark is provoked between two electrodes separated by a gap of substantially 0.6 mm, depend-ing on the sparking conditions. Ignition of the mixture is initiated by a cylindrical plasma the length of which is that of the gap between the electrodes. The plasma liberates energy by thermal conductivity and radiation and diffuses activated particles, these two actions being conducive to ignition of the carburated gas mixture and propagation of the flame.
Because of the relatively small dimensions of the plasma, the volume of the mixture concerned by the ignition is small compared to the total volume of gas to be ignited. This results in the well-known difficulties of ignition that occur firstly when the richness of the mixture to be ignited is very different from the stoichiometric mixture and secondly by the fact that the gaseous mixture is not sufficiently locally homo-geneous and that the plasma created being of small dimensions, can concern mixture zones the richness of which is very different from stoichiometric proportions.
It is known that elongation of the spark leads to higher amounts of energy liberated and transmitted by heat conduction of the gaseous medium and also to higher radiation ?
, ,~,~"
s~
intensity and density of the ionized particles.
Attempts have therefore been made for considerable time to find a way of extending the electrical ignition spark in order to increase the probability of finding along the path of the spark or plasma mix-ture zones that approach the stiochio-metric ratio, thus enabling a high performance and reliable ignition procedure to be obtained. Certain methods of elonga-tion the spark consist in increasing the yap between the electrodes and inserting an element between them acting as relay for the spark.
Patent FR 1 540 25~ describes such a device in which an intermediate element acting as relay for the spark is insert-ed half-way along the gap between the electrodes. The element is metallic, electrically insulated from the electrodes and carried by an insulator endowed with good thermal conductivity.
The total length of the spark produced attains 1.2 mm in this way.
In Patent FR 2 323 253, which concerns a plasma igniter for a gas turbine engine, the element inserted between the two electrodes is a cylindrical bar in semiconductor material such as a ferrite or ferrite doped with titanium bioxide, the ends of which are in mechanical and electrical contact with each of the electrodes respectively. The outer surface of the bar is insulated from the gaseous mixture by a coat of enamel, except For a longitudinal strip connecting the two electrodes providing a path for the spark. Here, it is thought that the semiconductor element brings about local preheating oF the mix-ture to be ignited causing the density of the gas to drop locally, thus making it easier for the spark to jump.
Another method for creating an arc discharge whose length is much longer than ordinary obtainable and whose length and disposition can be electronically controlled is disclosed
Known methods of electrical ignition consist in bring-ing about an electric spark at the appropriate moment in a gaseous medium in order under certain conditions to achieve ignition and to maintain combustion.
As a general rule, the spark is provoked between two electrodes separated by a gap of substantially 0.6 mm, depend-ing on the sparking conditions. Ignition of the mixture is initiated by a cylindrical plasma the length of which is that of the gap between the electrodes. The plasma liberates energy by thermal conductivity and radiation and diffuses activated particles, these two actions being conducive to ignition of the carburated gas mixture and propagation of the flame.
Because of the relatively small dimensions of the plasma, the volume of the mixture concerned by the ignition is small compared to the total volume of gas to be ignited. This results in the well-known difficulties of ignition that occur firstly when the richness of the mixture to be ignited is very different from the stoichiometric mixture and secondly by the fact that the gaseous mixture is not sufficiently locally homo-geneous and that the plasma created being of small dimensions, can concern mixture zones the richness of which is very different from stoichiometric proportions.
It is known that elongation of the spark leads to higher amounts of energy liberated and transmitted by heat conduction of the gaseous medium and also to higher radiation ?
, ,~,~"
s~
intensity and density of the ionized particles.
Attempts have therefore been made for considerable time to find a way of extending the electrical ignition spark in order to increase the probability of finding along the path of the spark or plasma mix-ture zones that approach the stiochio-metric ratio, thus enabling a high performance and reliable ignition procedure to be obtained. Certain methods of elonga-tion the spark consist in increasing the yap between the electrodes and inserting an element between them acting as relay for the spark.
Patent FR 1 540 25~ describes such a device in which an intermediate element acting as relay for the spark is insert-ed half-way along the gap between the electrodes. The element is metallic, electrically insulated from the electrodes and carried by an insulator endowed with good thermal conductivity.
The total length of the spark produced attains 1.2 mm in this way.
In Patent FR 2 323 253, which concerns a plasma igniter for a gas turbine engine, the element inserted between the two electrodes is a cylindrical bar in semiconductor material such as a ferrite or ferrite doped with titanium bioxide, the ends of which are in mechanical and electrical contact with each of the electrodes respectively. The outer surface of the bar is insulated from the gaseous mixture by a coat of enamel, except For a longitudinal strip connecting the two electrodes providing a path for the spark. Here, it is thought that the semiconductor element brings about local preheating oF the mix-ture to be ignited causing the density of the gas to drop locally, thus making it easier for the spark to jump.
Another method for creating an arc discharge whose length is much longer than ordinary obtainable and whose length and disposition can be electronically controlled is disclosed
- 2 -in U.S. Patent No. 3 974 ~12.
According to -this Patent, a spark plug comprises, in combination, a high voltage electrode that extends axially out-ward from the base of the spark plug, an insulating jacket covering said high voltage electrode extending continuously from the base of the plug to the region of the Free end of the ~igh ~ol~age electrode, the ~ree end of the high voltage electrode being exposed, the high voltage electrode at said free end being formed to have a sparking surface oriented at an angle to ~o the axially e~tending part o~ the high ~oltage axial electrode, a ground electrode extending from the body of the spark plug to the vicinity of the insulating jacket on the high voltage electrode and having a sparking surface oriented at an angle to said axis, there being a separation between the ground electrode and the high voltage electrode through the insulating jacket that is much less than the gap between the sparking sur~ace of the ground electrode and the sparking surface of the high voltage electrode, the sparking surface of the electrodes being properly tapered such that an arc formed in an operating spark plug follows a curved path meeting each tapered sparking surface along a direction such that the discharge bends away from said axially extending part, said arc varying in character in an out-ward radial direction from said axially extending part to pro-vide a distribution oF energy and temperature in the arc.
According to the teaching of this Patent non creeping spark arcs at most 1 cm long are obtainable.
The object of the invention is to provide substan-tially long sparks of say several cms. or tens of cms. long, said sparks being of the flash type.
A further object of the invention is to provide an arc whose path complies with any arbitrarily defined pattern.
A further object of the invention is to ensure electi-st7 cal ignition of a carburated gas mixture, even when this mixture is very lean and heterogeneous in space and time.
The invention provides means for ob-taining a spark distinctly greater in length to that of sparks previously obtain-ed, rendering it possible by causing this spark to slide on a dielectric surface of high resistivity, to be endowed with all shaped conducive to ready ignition of the mixture, regardless of the configuration and type of the combustion chamber.
The flash spark plug for igniting carburated gaseous mixtures according to the invention comprises a high voltage electrode, a ground electrode, a high resistivity dielectric elongated member, said dielectric member having a face exposed to said carburated gaseous mixture and the electrodes being in contact with said face and defining a dielectric gap thereon and means for applying a pulsed high voltage across said elec-trodes, charaterized in that it further comprises a conductive strip connected to said ground electrode, lying on the face of the dielectric plate opposite to said exposed face and terminat-ing in the region of said opposite face located substantially beneath said high voltage electrode.
According to the invention, a process to ignite a carburated gaseous mixture in a combustion chamber consists in inserting in. the wall of said combustion chamber a dielectric elongated member, securing to the face of said dielectric member exposed to said carburated gaseous mixture t~o electrodes defining on said face a dielectric gap on which a sliding spark is to be formed, applying across said electrodes a pulsed high voltage and it is characterized in that it further consists in forming a conductive path on the non-exposed face of the di-electric plate, said path originating at and having an endconnected to one of said electrode and terminating in the region located substantially beneath the other electrode, the shape of 5~7 said path being that of the sliding spark.
The invention is henceforth described with reference to the accompanying drawings in which:
Fig. 1 is a diagrammatic representation of a flash spark plug in accordance with the invention;
Fig. 2 is a prospective view in accordance with Fig.
;
Fig. 3 is a top view of Fig. 1 illustrating the electrical discharge mechanism;
Fig. 4 is a cross-sectional variant of the plug of Fig. 1 in accordance with the invention;
Figs. 5a and 5b are examples of application of the invention to the wall of a combustion chamber; and Fig. 6 is another example of application of the invention to a plasma igniter installed inside a turbojet combustion chamber.
On diagrammatic Figs. 1 and 2 a first cylindrical electrode 1 is connected to a high level pulsed voltage generator producing for instance 30 000 volts. One of the ends 10 of the electrode is placed in intimate contact with the upper surface 11 of a plate of dielectric material 12. A second electrode 2 at the edge of the dielectric plate and the end 20 of which is situated above the surface of the dielectric is grounded. Electrodes 1 and 2 are supplied by a high voltage generator assembly 21.
Electrode 2 is extended over the face 13 of the di-electric opposite face 11 as far as electrode 1 by a metal blade 14 the configuration of which corresponds to the path that is intended to cause the spark to follow.
Fig. 3 shows the design of an electrical discharge over a dielectric surface. The voltage of electrode 1 is in-creased from O to several tens of thousands of volts preferably ~, within a few microseconds, i.e. relatively slowly. The electric field created in the area around end 10 of electrode 1 becomes very extensive and procluces local ionization of the gaseous mixture. Raising the voltage causes a number of small highly ionized conductive filaments -to form shown as items 15 and which grow apace with the rise in vol-tage. The end oF the filaments results in a multiplicity of shorter diverting branch filaments equivalent to a cold corona discharge. Current runs in the filaments 15 and their temperature rises. Since they are conductive9 the electric field is shifted to the head 16 of the short filaments 16 which deposit positive charges on the surface of the dielectric. At the end oF the process, one of the ionized filaments 15 will encounter electrode 2 that is grounded short-circuiting the electric generator 21, which is protected by a series resistor. Consequently, a highly intense current wave rises from 2 towards 1 inside the filament concerned, heating it up considerably. The transient arc established receives almost all the available energy and can hence be set up over practically any length.
However, this mechanism gives relatively little satisfaction since in most cases only one of the filaments created will touch electrode 2 and the other filaments, which are very numberous directed in any direction, unnecessarily consume part of the energy available.
This is why an extension of the grounded electrode 2 is provided in the form of a metal blade or wire or layer laid a small distance from the dielectric plate surface on which the spark forms in order through the dielectric material to form filaments in such a way that only the useful filaments are form-ed and in accordance with a predetermined path that can be of any desired configuration.
Fig. 4 shows an alternative arrangement of Figs. 1 and 2 in which eletrode 2 is extended by a metal blade 1~1 inserted into the dielectric 12 parallel to face 11, forming the spark and set a distance of d from it. On this figure, -the positive charges deposited on the surface by filiments 15 and the nega-tive charges engendered by the extension 14 of the electrode 2 are shown, ensuring that an electric Field is set up inside the dielectric 12.
The bottom wall of the combustion chamber is hemi-spherical (Fig. 5a). On the inner face of this bottom wall, three curved metal strips 141, 142, and 143 in the shape of meridional lines on a sphere are deposited or otherwise secured thereto. These strips 141, 142, 143 are angularly spaced apart by 120. Ceramic costing 121, 122, 123 cover the metal strips which are folded around the edge of the ceramic coating, thus forming the electrodes 1021, 1022, 1023. The electrode 101 has three projection brances 1011, 1l2, 1013 radially aligned with electrodes 1021, 1022, 1023. The spark a star configuration.
In Fig. 5b~ the device in accordance with the invention is installed on the side wall of the combustion chamber or a 20 turbojet. The metal wall 50 of the chamber is machined out in order to house the igniter. The purpose is to obtain a very long spark at wall 50. The igniter has an electrode 201 raised to a high level pulsed voltage generated by the pulse generator 31, an electrode 202 secured to wall 50 connected to the ground-ing terminal of the pulse generator 21 and a dielectric piece 12 the surface 11 of which is the dielectric surface for forming the spark. Electrode 202 is extended by a metal guide 14 set parallel to surface 11. Guide 14 consists of a thin rectilinear blade enabling a spark to propagate in a straight line over 30 several tens of centimetres on surface 11 of electric 12.
Fig. 6 concerns another form of injection type igniter to ignite turbojets or ramjets. The igniter consists of a metal body 60 and means o-f securing it to wall 50 of -the combustion chamber. Electrode 301 is housed axially in the igniter inside an insulator 51 by a known technique and com-prising at its end a dielectric tubular body 12 resting on a grounding electrode 302. A conduit 61 enabling small quantities of combustible fuel to be introduced leads to the gap between the electrodes.
The internal surface 11 of the dielectric element is the surface on which the spark forms. The outer surface 13 of the dielectric is supported on a helical shoulder 314 machined into the body 60 of the igniter providing yuidance by inducing the spark to spread over the internal surface 11 of the di-electric as a helical spark.
As regards the dielectric materials used to implement the invention, these are selected from those available to the specialist in accordance with the methods of implementation specific to the invention. For instance, it will be possible to select alumina-based ceramic compositions or any equivalent material provided the requisite of high resistive of at least 10 ohms. cm, and preferably greater than 1012 ohms. cm is complied with.
Depending on the particular case, the dielectric element can be formed as an assembly with the grounded electrode and its metal extension and then the assembly can be secured to the wall of the chamber.
Contrarywise, it is possible in certain cases to form all the parts of the assembly directly on the wall using spray or sputtering deposit techniques, for instance with a plasma torch, both for the dielectric and for the metal extension of the grounding electrode.
r~S suggested by the description, the invention can be applied with advantage to all cases in which ignition of gaseous carburated rnixtures has to be brought about, regardless of the type and conforma~ion of the combus-tion chamber.
In order to fix one's ideas, a plug of the invention with a dielectric plate of 0.1 mm thick and having a resisti-vity oF 101 ohm. cms, and -Fed by a 30 kV pulse voltage allows a spark of 3 cms to be ignited in a gas under a pressure of 10 atmospherics9 while prior art plug sparks do not exceed significantly the Paschen's law value of ~.1 cm.
Although only two shapes of creeping sparks have been disclosed in the foregoing, namely a divergent multibranch creeping spark and a single branch helical creeping spark, every desired configuration of spark can be implemented accord-ing to the invention. Particularly parallel multi-branch sparks originating at a common active electrode and terminating at a common ground electrode can be readily built up. As an examplea such a spark can comprise a First rectilinear branch, a second V-shaped branch and a third inverted V-shaped branch.
g ~'
According to -this Patent, a spark plug comprises, in combination, a high voltage electrode that extends axially out-ward from the base of the spark plug, an insulating jacket covering said high voltage electrode extending continuously from the base of the plug to the region of the Free end of the ~igh ~ol~age electrode, the ~ree end of the high voltage electrode being exposed, the high voltage electrode at said free end being formed to have a sparking surface oriented at an angle to ~o the axially e~tending part o~ the high ~oltage axial electrode, a ground electrode extending from the body of the spark plug to the vicinity of the insulating jacket on the high voltage electrode and having a sparking surface oriented at an angle to said axis, there being a separation between the ground electrode and the high voltage electrode through the insulating jacket that is much less than the gap between the sparking sur~ace of the ground electrode and the sparking surface of the high voltage electrode, the sparking surface of the electrodes being properly tapered such that an arc formed in an operating spark plug follows a curved path meeting each tapered sparking surface along a direction such that the discharge bends away from said axially extending part, said arc varying in character in an out-ward radial direction from said axially extending part to pro-vide a distribution oF energy and temperature in the arc.
According to the teaching of this Patent non creeping spark arcs at most 1 cm long are obtainable.
The object of the invention is to provide substan-tially long sparks of say several cms. or tens of cms. long, said sparks being of the flash type.
A further object of the invention is to provide an arc whose path complies with any arbitrarily defined pattern.
A further object of the invention is to ensure electi-st7 cal ignition of a carburated gas mixture, even when this mixture is very lean and heterogeneous in space and time.
The invention provides means for ob-taining a spark distinctly greater in length to that of sparks previously obtain-ed, rendering it possible by causing this spark to slide on a dielectric surface of high resistivity, to be endowed with all shaped conducive to ready ignition of the mixture, regardless of the configuration and type of the combustion chamber.
The flash spark plug for igniting carburated gaseous mixtures according to the invention comprises a high voltage electrode, a ground electrode, a high resistivity dielectric elongated member, said dielectric member having a face exposed to said carburated gaseous mixture and the electrodes being in contact with said face and defining a dielectric gap thereon and means for applying a pulsed high voltage across said elec-trodes, charaterized in that it further comprises a conductive strip connected to said ground electrode, lying on the face of the dielectric plate opposite to said exposed face and terminat-ing in the region of said opposite face located substantially beneath said high voltage electrode.
According to the invention, a process to ignite a carburated gaseous mixture in a combustion chamber consists in inserting in. the wall of said combustion chamber a dielectric elongated member, securing to the face of said dielectric member exposed to said carburated gaseous mixture t~o electrodes defining on said face a dielectric gap on which a sliding spark is to be formed, applying across said electrodes a pulsed high voltage and it is characterized in that it further consists in forming a conductive path on the non-exposed face of the di-electric plate, said path originating at and having an endconnected to one of said electrode and terminating in the region located substantially beneath the other electrode, the shape of 5~7 said path being that of the sliding spark.
The invention is henceforth described with reference to the accompanying drawings in which:
Fig. 1 is a diagrammatic representation of a flash spark plug in accordance with the invention;
Fig. 2 is a prospective view in accordance with Fig.
;
Fig. 3 is a top view of Fig. 1 illustrating the electrical discharge mechanism;
Fig. 4 is a cross-sectional variant of the plug of Fig. 1 in accordance with the invention;
Figs. 5a and 5b are examples of application of the invention to the wall of a combustion chamber; and Fig. 6 is another example of application of the invention to a plasma igniter installed inside a turbojet combustion chamber.
On diagrammatic Figs. 1 and 2 a first cylindrical electrode 1 is connected to a high level pulsed voltage generator producing for instance 30 000 volts. One of the ends 10 of the electrode is placed in intimate contact with the upper surface 11 of a plate of dielectric material 12. A second electrode 2 at the edge of the dielectric plate and the end 20 of which is situated above the surface of the dielectric is grounded. Electrodes 1 and 2 are supplied by a high voltage generator assembly 21.
Electrode 2 is extended over the face 13 of the di-electric opposite face 11 as far as electrode 1 by a metal blade 14 the configuration of which corresponds to the path that is intended to cause the spark to follow.
Fig. 3 shows the design of an electrical discharge over a dielectric surface. The voltage of electrode 1 is in-creased from O to several tens of thousands of volts preferably ~, within a few microseconds, i.e. relatively slowly. The electric field created in the area around end 10 of electrode 1 becomes very extensive and procluces local ionization of the gaseous mixture. Raising the voltage causes a number of small highly ionized conductive filaments -to form shown as items 15 and which grow apace with the rise in vol-tage. The end oF the filaments results in a multiplicity of shorter diverting branch filaments equivalent to a cold corona discharge. Current runs in the filaments 15 and their temperature rises. Since they are conductive9 the electric field is shifted to the head 16 of the short filaments 16 which deposit positive charges on the surface of the dielectric. At the end oF the process, one of the ionized filaments 15 will encounter electrode 2 that is grounded short-circuiting the electric generator 21, which is protected by a series resistor. Consequently, a highly intense current wave rises from 2 towards 1 inside the filament concerned, heating it up considerably. The transient arc established receives almost all the available energy and can hence be set up over practically any length.
However, this mechanism gives relatively little satisfaction since in most cases only one of the filaments created will touch electrode 2 and the other filaments, which are very numberous directed in any direction, unnecessarily consume part of the energy available.
This is why an extension of the grounded electrode 2 is provided in the form of a metal blade or wire or layer laid a small distance from the dielectric plate surface on which the spark forms in order through the dielectric material to form filaments in such a way that only the useful filaments are form-ed and in accordance with a predetermined path that can be of any desired configuration.
Fig. 4 shows an alternative arrangement of Figs. 1 and 2 in which eletrode 2 is extended by a metal blade 1~1 inserted into the dielectric 12 parallel to face 11, forming the spark and set a distance of d from it. On this figure, -the positive charges deposited on the surface by filiments 15 and the nega-tive charges engendered by the extension 14 of the electrode 2 are shown, ensuring that an electric Field is set up inside the dielectric 12.
The bottom wall of the combustion chamber is hemi-spherical (Fig. 5a). On the inner face of this bottom wall, three curved metal strips 141, 142, and 143 in the shape of meridional lines on a sphere are deposited or otherwise secured thereto. These strips 141, 142, 143 are angularly spaced apart by 120. Ceramic costing 121, 122, 123 cover the metal strips which are folded around the edge of the ceramic coating, thus forming the electrodes 1021, 1022, 1023. The electrode 101 has three projection brances 1011, 1l2, 1013 radially aligned with electrodes 1021, 1022, 1023. The spark a star configuration.
In Fig. 5b~ the device in accordance with the invention is installed on the side wall of the combustion chamber or a 20 turbojet. The metal wall 50 of the chamber is machined out in order to house the igniter. The purpose is to obtain a very long spark at wall 50. The igniter has an electrode 201 raised to a high level pulsed voltage generated by the pulse generator 31, an electrode 202 secured to wall 50 connected to the ground-ing terminal of the pulse generator 21 and a dielectric piece 12 the surface 11 of which is the dielectric surface for forming the spark. Electrode 202 is extended by a metal guide 14 set parallel to surface 11. Guide 14 consists of a thin rectilinear blade enabling a spark to propagate in a straight line over 30 several tens of centimetres on surface 11 of electric 12.
Fig. 6 concerns another form of injection type igniter to ignite turbojets or ramjets. The igniter consists of a metal body 60 and means o-f securing it to wall 50 of -the combustion chamber. Electrode 301 is housed axially in the igniter inside an insulator 51 by a known technique and com-prising at its end a dielectric tubular body 12 resting on a grounding electrode 302. A conduit 61 enabling small quantities of combustible fuel to be introduced leads to the gap between the electrodes.
The internal surface 11 of the dielectric element is the surface on which the spark forms. The outer surface 13 of the dielectric is supported on a helical shoulder 314 machined into the body 60 of the igniter providing yuidance by inducing the spark to spread over the internal surface 11 of the di-electric as a helical spark.
As regards the dielectric materials used to implement the invention, these are selected from those available to the specialist in accordance with the methods of implementation specific to the invention. For instance, it will be possible to select alumina-based ceramic compositions or any equivalent material provided the requisite of high resistive of at least 10 ohms. cm, and preferably greater than 1012 ohms. cm is complied with.
Depending on the particular case, the dielectric element can be formed as an assembly with the grounded electrode and its metal extension and then the assembly can be secured to the wall of the chamber.
Contrarywise, it is possible in certain cases to form all the parts of the assembly directly on the wall using spray or sputtering deposit techniques, for instance with a plasma torch, both for the dielectric and for the metal extension of the grounding electrode.
r~S suggested by the description, the invention can be applied with advantage to all cases in which ignition of gaseous carburated rnixtures has to be brought about, regardless of the type and conforma~ion of the combus-tion chamber.
In order to fix one's ideas, a plug of the invention with a dielectric plate of 0.1 mm thick and having a resisti-vity oF 101 ohm. cms, and -Fed by a 30 kV pulse voltage allows a spark of 3 cms to be ignited in a gas under a pressure of 10 atmospherics9 while prior art plug sparks do not exceed significantly the Paschen's law value of ~.1 cm.
Although only two shapes of creeping sparks have been disclosed in the foregoing, namely a divergent multibranch creeping spark and a single branch helical creeping spark, every desired configuration of spark can be implemented accord-ing to the invention. Particularly parallel multi-branch sparks originating at a common active electrode and terminating at a common ground electrode can be readily built up. As an examplea such a spark can comprise a First rectilinear branch, a second V-shaped branch and a third inverted V-shaped branch.
g ~'
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A flash-spark plug device for igniting carburated gaseous mixtures comprising a high voltage electrode, at least a ground electrode, at least a high resistivity dieletric elongated member, said dielectric member having a face exposed to said carburated gaseous mixture and means for applying a pulsed high voltage across said electrodes, in which the electrodes are in intimate contact with said face and define a dielectric gap thereon, and that the plug device comprises at least a conductive strip connected to said ground electrode, lying on the face of the dielectric member opposite to said exposed face and terminating in the region of said face located substantially beneath said high voltage electrode.
2. A device according to claim 1, in which the dielectric elongated member is a dielectric rectangular plate and the ground electrode is located at one edge of said plate and is folded around said edge for contacting said conductive strip on said opposite face.
3. A device according to claim 1, in which the dielectric elongated member is a dielectric tubular member having its inner face exposed to the carburated gaseous mixture and said high voltage electrode and ground electrode being in intimate contact with the respective ends of the dielectric tubular member and the conductive strip is a helical strip on the outer face of said tubular member.
4. A device according to claim 1 comprising a plurality of ground electrodes, a single dielectric member, the high voltage electrode and all the ground electrodes being in intimate contact with the face of the dielectric member exposed to the carburated gaseous mixture, characterized in that it further comprises a plurality of conductive strips lying on the face of the dielectric member opposite to the exposed faces and respectively connected to the ground electrodes.
5. A device according to claim 4, in which that the conductive strips are equi-angularly spaced apart around the region of said opposite face just beneath the high voltage electrode, whereby the flash spark has a star configuration.
6. A device according to claim 1, comprising a first plurality of ground electrodes, a second plurality, equal to the first, of dielectric elongated members, the high voltage electrode and all the ground electrodes being in intimate contact with respectively the faces of the dielectric members exposed to the carburated mixture characterized in that it further comprises a third plurality, equal to the first and second pluralities, of conductive strips respectively lying on the faces of the dielectric members opposite to the exposed faces thereof and respectively connected to the ground electrodes.
7. A device according to claim 6, in which the conductive strips are equi-angularly spaced apart around the region of said opposite faces just beneath the high voltage electrode, whereby the flash-spark has a star configuration.
8. A device according to claim 1, in which the gap defined by the electrodes on the dielectric member is at least 3 centimetres long and the means for applying a pulsed high voltage across the high voltage and ground electrodes has a voltage of at least 30 kilovolts.
9. A process for manufacturing a flash-spark plug device for igniting a carburated gaseous mixture in a combustion chamber which comprises inserting in the wall of said combustion chamber a dielectric elongated member and securing to the face of said dielectric member exposed to said carburated gaseous mixture two electrodes defining on said face a dielectric gap on which a creeping spark is to be formed, and forming a conductive path on the non-exposed face of the dielectric member, said path originating at and having an end connected to one of said electrodes and terminating in the region located substantially beneath the other electrode, the shape of said path being that of the creeping spark.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8027717A FR2497273B1 (en) | 1980-12-29 | 1980-12-29 | METHOD AND DEVICE FOR IGNITION OF A FUEL MIXTURE |
| FR80-27717 | 1980-12-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1182857A true CA1182857A (en) | 1985-02-19 |
Family
ID=9249581
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000393083A Expired CA1182857A (en) | 1980-12-29 | 1981-12-23 | Ignition method and igniter device for ignition carburated gaseous mixtures |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4525140A (en) |
| EP (1) | EP0055658B1 (en) |
| JP (1) | JPS57136027A (en) |
| CA (1) | CA1182857A (en) |
| CS (1) | CS273306B2 (en) |
| DE (1) | DE3173158D1 (en) |
| FR (1) | FR2497273B1 (en) |
| PL (1) | PL137486B1 (en) |
| SU (1) | SU1074424A3 (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3544176C1 (en) * | 1985-12-13 | 1987-05-21 | Beru Werk Ruprecht Gmbh Co A | Spark plug with combined sliding and air spark gaps |
| US5046466A (en) * | 1990-09-20 | 1991-09-10 | Lipski Frank F | Spark-ignition engine |
| US5587630A (en) * | 1993-10-28 | 1996-12-24 | Pratt & Whitney Canada Inc. | Continuous plasma ignition system |
| US5659132A (en) * | 1995-03-07 | 1997-08-19 | Fel-Pro Incorporated | Gasket enclosed sensor system |
| FR2816119B1 (en) * | 2000-10-27 | 2003-02-21 | Renault | RADIAL SPARKLE SURFACE CANDLE |
| US6532737B1 (en) | 2001-08-30 | 2003-03-18 | Dana Corporation | Exhaust port gasket with cylinder-specific electronic oxygen sensors |
| US6883507B2 (en) * | 2003-01-06 | 2005-04-26 | Etatech, Inc. | System and method for generating and sustaining a corona electric discharge for igniting a combustible gaseous mixture |
| US20050019714A1 (en) * | 2003-07-24 | 2005-01-27 | David Platts | Plasma catalytic fuel injector for enhanced combustion |
| CA2669438C (en) * | 2006-04-24 | 2015-06-16 | Axcelon Biopolymers Corporation | Nanosilver coated bacterial cellulose |
| US20090151322A1 (en) * | 2007-12-18 | 2009-06-18 | Perriquest Defense Research Enterprises Llc | Plasma Assisted Combustion Device |
| FR2932229B1 (en) * | 2008-06-05 | 2011-06-24 | Renault Sas | CONTROL OF THE POWER SUPPLY OF AN IGNITION CANDLE OF AN INTERNAL COMBUSTION ENGINE |
| FR2960913B1 (en) * | 2010-06-04 | 2012-07-13 | Snecma | PREHEATING AN IGNITION CANDLE |
| US20130300278A1 (en) * | 2012-05-11 | 2013-11-14 | Uci/Fram Group | Fouling resistant spark plug |
| US10030583B2 (en) * | 2013-02-21 | 2018-07-24 | United Technologies Corporation | Distributed spark igniter for a combustor |
| US20150059314A1 (en) * | 2013-08-29 | 2015-03-05 | Digital Solid State Propulsion, Inc. | Electrically ignited and throttled pyroelectric propellant rocket engine |
| US10992112B2 (en) | 2018-01-05 | 2021-04-27 | Fram Group Ip Llc | Fouling resistant spark plugs |
Family Cites Families (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB191022517A (en) * | 1909-09-29 | Riese Walter | Improvements in and relating to Electrical Ignition Appliances. | |
| US2208668A (en) * | 1940-02-16 | 1940-07-23 | Devine Julius | Aviation spark plug |
| DE885031C (en) * | 1942-10-02 | 1953-07-30 | Nienburger Metallwarenfabrik A | Spark plug |
| US2605754A (en) * | 1947-10-04 | 1952-08-05 | Smitsvonk Nv | Low-tension ignition spark plug for condenser discharge |
| FR1056336A (en) * | 1951-03-02 | 1954-02-25 | Smitsvonk Nv | Superficial discharge spark plug for low voltage and capacitor discharge |
| US2745980A (en) * | 1952-03-03 | 1956-05-15 | Smitsvonk N V Res Lab Comp | Surface discharge plug for low tension and condenser discharge |
| NL105200C (en) * | 1952-10-06 | |||
| DE1197154B (en) * | 1960-04-28 | 1965-07-22 | Leonard Joseph Melhart | Contactless device for generating and extinguishing short-term high-current arcs |
| US3202859A (en) * | 1961-11-08 | 1965-08-24 | Mallory Res Co | Spark plug |
| US3439995A (en) * | 1966-09-30 | 1969-04-22 | Crown Sangyo Kk | Spark ignited gas burner |
| FR1540265A (en) * | 1966-11-03 | 1968-09-27 | Inst Francais Du Petrole | New spark plug for internal combustion engines |
| US3581141A (en) * | 1969-04-07 | 1971-05-25 | Ethyl Corp | Surface gap spark plug |
| GB1510468A (en) * | 1974-11-04 | 1978-05-10 | Smiths Industries Ltd | Igniters |
| US3974412A (en) * | 1975-02-03 | 1976-08-10 | Massachusetts Institute Of Technology | Spark plug employing both corona discharge and arc discharge and a system employing the same |
| GB1572339A (en) * | 1975-07-08 | 1980-07-30 | Johnson Matthey Co Ltd | Igniters suitable for gas turbines |
| FR2321791A1 (en) * | 1975-08-22 | 1977-03-18 | Le Polt I | Heavy current controlled discharge path - has dielectric element with two main and one control electrodes on one side |
| GB1544203A (en) * | 1975-09-08 | 1979-04-11 | Smiths Industries Ltd | Electrical igniters |
| US4142121A (en) * | 1975-09-08 | 1979-02-27 | Smiths Industries Limited | Electrical igniters |
| JPS5349643A (en) * | 1976-10-19 | 1978-05-06 | Ngk Spark Plug Co Ltd | Rear electrode type spark plug with long discharge gap |
| US4264844A (en) * | 1978-09-29 | 1981-04-28 | Axe Gavin C H | Electrical igniters |
| JPS55155092U (en) * | 1979-04-23 | 1980-11-08 | ||
| US4418300A (en) * | 1980-01-17 | 1983-11-29 | Mitsubishi Denki Kabushiki Kaisha | Metal vapor discharge lamp with heat insulator and starting aid |
-
1980
- 1980-12-29 FR FR8027717A patent/FR2497273B1/en not_active Expired
-
1981
- 1981-12-17 EP EP81402023A patent/EP0055658B1/en not_active Expired
- 1981-12-17 DE DE8181402023T patent/DE3173158D1/en not_active Expired
- 1981-12-22 US US06/333,272 patent/US4525140A/en not_active Expired - Fee Related
- 1981-12-23 CA CA000393083A patent/CA1182857A/en not_active Expired
- 1981-12-28 SU SU813368429A patent/SU1074424A3/en active
- 1981-12-28 JP JP56210069A patent/JPS57136027A/en active Granted
- 1981-12-29 CS CS994381A patent/CS273306B2/en unknown
- 1981-12-29 PL PL1981234488A patent/PL137486B1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57136027A (en) | 1982-08-21 |
| EP0055658B1 (en) | 1985-12-04 |
| CS273306B2 (en) | 1991-03-12 |
| JPS6316644B2 (en) | 1988-04-11 |
| CS994381A2 (en) | 1990-08-14 |
| PL234488A1 (en) | 1982-07-19 |
| SU1074424A3 (en) | 1984-02-15 |
| DE3173158D1 (en) | 1986-01-16 |
| US4525140A (en) | 1985-06-25 |
| FR2497273B1 (en) | 1985-09-20 |
| PL137486B1 (en) | 1986-06-30 |
| FR2497273A1 (en) | 1982-07-02 |
| EP0055658A1 (en) | 1982-07-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |